Method of preparing metal blanks for drawing



sept. 26, 1961 G. A. LYON 3,001,278

METHOD OF PREPARING METAL BLANKS FOR DRAWING Filed Nov. 25, 1955 l .FE :r1 ZLDT George Albert Lyon Unite The present invention relates to improvements in preparatlon of metal blanks for drawing or like fabrication where a generally circular outline is desirable in the blank. Where metallic blanks of substantial thickness are to be drawn into shell form, it is desirable to trim the same into circular shape before drawing so as to have substantially equal elongation in the radially outer or marginal portion of the blank that is turned to provide the tubular wall of the shell. Where such blanks arederived from rolled strip cut into polygonal pieces such as square, substantial waste is experienced where the corner portions of the polygonal blank are trimmed off to provide the circular blank.

It is an important object of the present invention to provide a novel method of preparing blanks.` of circular outline from polygonally shaped blanks of metal plate. Another object of the invention is to provide an improved method of transforming polygonally shaped metal rates Patent M' plate blanks into circular blanks without wasting material.

A further object of the invention is to provide an improved method of transforming a polygonally shaped metal blank into a circular blank adapted for drawing, and whereby all of the material of the polygonal blank is utilized in the circular blank.

Other objects, features and advantages of the present invention will be readily apparent from the following detailed description of a preferred embodiment thereof 3,@@1278 Patented Sept. 26, 1961 ECC According to the present invention, scrap loss is eliminated although round blanks are derived from square, or other polygonally shaped slabs or billets cut from rolled strip. .To this end, referring to 'FIGURES 1 and 2, a polygonal slab blank v10 is provided, for example, in square shape, and having a mass calculated to afford the. amount of material required to be provided in a round blank to attain the desired results as to mass and dimensions in a drawn shell to be fabricated from the blank. The dimensions between the sides of the blank will beless than the ultimate diameter of the round blank, although the dimension between the opposite corners of the blank will be slightly greater. As shown in FlG- URE l, the blank has four corners C. By way of vcomparison, there has been superimposed upon FIGURE 1 a phantom circular outline depicting the diameter of the ultimate round blank desired to be derived from the initially square blank 10, having regard tol the thickness and square dimensions of the blank. It will be observed that the diametrical differentials between the round outline and the square blank indicate that material in the corner portions C of the square blank 1t) compensate for the smaller dimension between the sides of the square blank than the diameter of the circle.

B-y the present invention, the material from the corners C of the blank is redistributed into the sid-e areas of the blank to produce a circular periphery for the blank. Herein this is accomplished by either hot or cold dishing of the blank .10 to draw the corners C uniformly radially inwardly into the periphery of the desired circular perimeter. The shape thus assumed by the blank 10 is shown in FIG. 3.

taken in conjunction with the accompanying drawing, in

which:

FIGURE 1 is a plan view of a polygonal metal blank adapted to be subjected to the method of the instant invention;

`FIGURE 2. is an edge elevational view of the blank of FIGURE 1; l

FIGURE 3 is a diametrical vertical sectional v-iew through a blank shaping die member and the blank of 4FIGURES 1 and 2 Shaped to be accommodated in the d ie member;

FIGURE 4 is a diametrical vertical sectional view vshowing the die member of LFIGURE 3 and a cooperating die member in the relationship thereof whereinthe blank has been converted into a round blank; and

yFIGURE 5 is a plan view of the blank of FIGURE 1 following transformation thereof in the die structure of 'FIGURES 3 and 4.

In the manufacture of shells, and more particularly shells of substantial size by drawing the shells from disk ,blanks of metal, rolled plate or strip material may be used. IWhere such material is of substantial thickness, it is generally more convenient to cut the strip or plate into polygonal blanks, such as square blanks prior to trimming the same into round form. To do so, however, rcquires the provision of a sudcient minimum dimension in the blank to allow for deriving the full diameter of the round blank desired from the polygonal shape, with scrap entirely about the round perimeter. It will thus be appreciated that a large amount of scrap is produced as waste. Where large size blanks are used, as for example in the production of ordnance shells, tanks and the like requiring metal blanks and more particularly steel blanks of 30" to 40 in diameter and up to 1% thick, the amount of scrap produced in thus deriving round blanks quickly reaches -a very large tonnage in mass production.

Then the dished blank is placed with its corners C within the encircling wall of a cavity 1d in ablank Vreshaping die lf2. The encircling Wall of the cavity is of the circular diameter which is to be assumed by the blank. The bottom of the cavity 11 may be provided by a stripper plunger 13, or at least` a portion of the bottom of the cavity may be so provided.

`Cooperatively related in relatively reciprocably interengageable and releasable relation to the die member 12 is a male die member or compression punch 14 having a complementary blank-shaping nose portion 15 adapted to tit down into the mouth of the shaping cavity 11. VLaterally adjacent to the nose portion 15 of the die member or punch 14 is stop structure 17 which limits projection of the nose 15 into the cavity 11 to the thickness of the formed blank. Such thickness may be substantially the same as the original thickness of the blank l0. Thus', as the dished blank 10 is pressed down into the cavity 11, the material in the corner portions C of the blank confined within the circumscribing circular wall of the cavity 11 is redistributed laterally into what were the Straight sides of the blank 10 which are thus laterally expanded to the perimeter deiined by the die cavity wall, as the blank 10 is flattened between the die members 12 and 14 as shown in FIGURE 4.

After the blank has been flattened and provided with a circular periphery conforming to the circular periphery of the cavity 11, and the die member 14 has been backed off, the blank is ejected by operation of the stripper 13. To facilitate stripping, the circular wall of the die cavity 11 is preferably tapered outwardly as shown. This is also beneficial in providing the blank with a correspondingly bevel edge to facilitate subsequent capping and drawing elongation without, or at least a minimum of, trimming required in such operations.

With certain grades of steel, especially, it is desirable to heat the blank 10 at least following the dishing thereof preparatory to the flattening and circularization to heat the same to a good plasticizing temperature. Since the blank 10 has been subjected to a certain amount of working in dishing it from the flat rolled material to the form shown in FIGURE 3, the temperature to which the steel piece should be brought, if it has not already been brought to a suicient temperature through the dishing operation, should be somewhat above the critical terupeature to enable the reworking of the blank to the at round form with the production of a uniform fine grain structure advantageous for subsequent cupping and drawing. For instance, the blank may be heated from l500 F. to 2000 F., depending upon the grade or composition of the steel.

If convenient, immediately after the blank has been flattened into the round form as shown in FIGURE S, and while it is still hot, it may be cupped and at least partially drawn, thus taking advantage of the softness of the material. lf it is desired to cold work the round blank into cupped form and then draw it into the shell form, it may be preferred to allow the flattened blank to anneal slowly, or evento subject the same to further annealing temperature if during the working of the blank to the attened condition the temperature drops below soft annealing temperature.

It will be understood that modifications and variations may be eifected without departing from the scope of the novel concepts of the present invention.

I claim as my invention:

l. ln a method of reshaping a metal blank of polygonal outline into a circular outline of a diameterl less than the dimension between opposite corners of the blank, dishing the blank to draw the corners radially inwardly and thereby reposition the corners of the blank within the diameter of said circular outline, and then compressing the blank axially into flattened form while confining the corners within the perimeter of said circular outline to thereby redistribute the material from the corner portions f the blank into a circular margin having a perimeter conforming to said circular outline.

2'. In a method of reshaping a flat rolled blank of polygonal outline into a circular outline of smaller diameter than the distance between opposite corners of the blank, dishing the blank to draw the corners radially inwardly within such circular outline, and then flattening the blank while connning the corners to said circular outline and redistributing the marginal areas of the blank into said circular outline to afford a conforming circular perimeter for the blank. 3. In a method of reshaping a polygonally shaped steel flat blank into a circular outline of a diameter less than the dimension between opposite corners of the blank, dishing the blank to draw the corners of the blank radially inwardly into said circular outline, and then while confining the corners of the blank within a circular die conforming to said circular outline and with the blank at working heat pressing the blank into attened condition and reworking the blank margin including said corners into circular perimeter conforming to said die.

4. In a method of reshaping a polygonally shaped steel flat blank into a circular outline of a diameter less than the dimension between opposite corners of the blank, dishing the blank to draw the corners of the blank radially inwardly into said circular outline, then while coniining the corners of the blank within a circular die conforming to said circular outline and with the blank at working heat pressing the blank into flattened condition and reworking the blank margin including said corners into circular perimeter conforming to said die, and while working the perimeter into said circular outline, imparting a bevel to the blank perimeter.

5. In a method of reshaping polygonal flat blanks of i metal into circular flat blanks of smaller diameter than the dimension between opposite corners of the blank, dishing the blank to draw the corners radially inwardly into said circular outline, placing the blank within a die cavity having a circular wall conforming to said circular outline and with the corners of the blank opposing said wall, and then pressing said blank into said cavity to rework `the corner portions and adjacent marginal portions of the blank into circular perimeter conforming to said die wall. 'v

6. Ina method of reshaping a metal blank of polygf onal outline having four corners into a circular outline of a diameter less than the dimension between opposite corners of the blank, dishing the blank to reduce the distance between the opposed corners to reposition the corners of the blank within the diameter of said circular outline, and then compressing the dished portion of the blank axially into ilattened form while conning the four corners within the perimeter of said circular outline to thereby redistribute the-material of the blank into a circular margin having a perimeter conforming to said circular outline.

7. In a method of reshaping a metall blank of polyg-A onal outline having `four corners into -a circular outline of a diameter less than the dimension between opposite corners of the blank, dishing the blank to reduce the dis'- tance between the opposed corners to reposition the corners of the blank within the diameter of said circular outline and to dispose the marginal edges of the blank vin angular relation to the axis of the blank through the dished portion, and then compressing the dished portion of the blank axially into ilattened form while conlining the four corners defined by the angular edges within the perimeter of said circular outline to thereby redistribute the material of the blank into circular nat form having a circular margin having a perimeter conjforrning to said 'circular outline.

References Cited in` the le of this patent I UNITED STATES PATENTS 

